(Not applicable)
(1) Field of the Invention
The present invention relates generally to drywall construction, and more particularly to improved corner bead and trim products formed of vinyl with knurling on exterior faces of the legs and a method of manufacturing the products.
(2) Background Information
Current building construction utilizes sheets of drywall, commonly referred to as xe2x80x9cwallboard,xe2x80x9d to form the surfaces of interior walls of buildings. Drywall is typically formed of sheets of plaster sheathed in an outer wrapping of heavy construction paper.
In drywall construction, joints between adjacent sheets of drywall are usually covered by a paper tape extending lengthwise along the joint. To finish exterior corners in wallboard construction, metal corner beads and bullnose beads are typically installed. Similarly, metal trim is used to protect and finish a wallboard edge at window and door jams, while expansion joints are inserted between sheets of wallboard at predetermined intervals within buildings.
The above-described corner bead and trim products include metal flanges projecting outwardly, which are perforated with circular holes or elongated slots, so that the trim product may be fastened to the drywall panels using nails or the like. Wet plaster is then smoothed into place to cover the metal flanges, and edges of the plaster are smoothed and feathered to cover and conceal the metal edges.
Corner bead and other drywall trim products of the prior art have also been extruded from plastic. However, these plastic bead and trim products suffer several drawbacks. First, it is very difficult to adhere plaster to the plastic material of the bead and trim products. For this reason, prior art configurations of plastic trim products utilize grooves or perforations through the legs of the trim products to assist in retaining or xe2x80x9cgrippingxe2x80x9d plaster.
However, both variations of these xe2x80x9cgrippingxe2x80x9d configurations have problems. The grooved plastic extrusions utilize grooves that extend lengthwise along the length of the bead or trim product, so that they may be formed during the extrusion of the product. This forms grooves that are oriented vertically when the product is applied to drywall. Vertically oriented grooves are a problem because gravity will cause the wet plaster material to slide downwardly along the grooves, rather than being supported in position.
While the configuration of bead and trim products with perforations does a better job of holding plaster material when oriented vertically, such perforations also permit the plaster to pass completely through the flanges and then mushroom out under the flanges. This mushrooming of the plaster behind the flanges pushes the flanges outwardly away from the drywall, forming an unsightly slightly rolling surface. In addition, the use of perforations requires additional plaster or xe2x80x9cmud,xe2x80x9d in order to fill the cavities formed by the perforations.
Finally, plastic trim products with apertures or perforations will typically require two coats of plaster to completely finish a joint. The first coat may cause xe2x80x9crollingxe2x80x9d in those locations where the flange is pushed slightly away from the drywall, which must be leveled out with a subsequent coat of plaster. In the alternative, once the mud dries, the mud within the perforations in the flange will settle out, leaving concave dimples in the surface, which must be filled and smoothed with a second coat of mud.
It is therefore a general object of the present invention to provide an improved vinyl corner bead that will retain joint compound in position on the bead legs when the products are oriented vertically.
Another object of the present invention is to provide an improved corner bead that requires less joint compound during finishing than prior art corner bead with perforated legs.
These and other objects will be apparent to those skilled in the art.
The corner bead of the present invention includes an elongated strip of plastic material with a central arcuate nose and a pair of flanges extending outwardly from the nose. The outward faces of the flanges have knurling formed thereon, to retain joint compound in place during dressing of the corner. In the preferred form of the invention, the knurling is in the form of diamond-shaped depressions formed uniformly across the length and width of the flange outward faces.